Titanium compounds

ABSTRACT

A titanium chelate which is the reaction product of either ethylene glycol, propylene glycol or diethylene glycol or of mixtures thereof with monoethanolamine and a titanium orthoester. The chelate is of use in producing stable suspensions of titanium dioxide in water.

United States Patent Brook et al.

[ 1 July 25,1972

[54] TITANIUM COMPOUNDS [72] inventors: David Whiteley Brook, Teesside;Raymond Ward, Coxhoe, both of England British Titan Products CompanyLimited, Durham, England [22] Filed: March 9,1970

[21] Appl.No.: 17,939

[73] Assignee:

[30] Foreign Application Priority Data March 18, 1969 Great Britain..14,048/69 [52] US. Cl. ..260/429.5, 106/300, 106/308 Q 2,894,9667/1959 Russell 260/429.5

2,920,089 l/1960 Samour.. .....260/429.5

3,028,297 4/1962 Legally ..260/429.5 X

OTHER PUBLICATIONS Chemical Abstracts, Vol. 52, pg. 6673b 1958) ChemicalAbstracts, Vol. 68, 56105, 1968) Primary Examiner-Tobias E. LevowAssistant ExaminerH. M. S. Sneed A!t0rne v--Birch, Swindler, McKie &Beckett [57] ABSTRACT A titanium chelate which is the reaction productof either ethylene glycol, propylene glycol or diethylene glycol or ofmixtures thereof with monoethanolamine and a titanium orthoester. Thechelate is of use in producing stable suspensions of titanium dioxide inwater.

6 Claims, No Drawings TITANIUM COMPOUNDS This invention relates totitanium compounds and particularly to titanium chelates which aresuitable for use for forming gels in aqueous media or for use asdispersants or suspending agents for materials in aqueous media.

The formation of chelates from organic titanium orthoesters with anumber of compounds is known. For instance, it is known to producechelates from alkanolamines and titanium orthoesters and that suchcompounds produce a gel when mixed with aqueous media. However, it hasbeen observed that a chelate prepared from monoethanolamine and atitanium orthoester is unstable when mixed with water in that itprecipitates a hydrous form of titanium dioxide and is too reactive foruse to produce stable gels.

Accordingly, a titanium chelate comprises the reaction product ofethylene glycol, propylene glycol or diethylene glycol andmonoethanolamine and a titanium orthoester.

it has been found that the chelates prepared from monoethanolamine,titanium orthoester and ethylene glycol, propylene glycol or diethyleneglycol are substantially water stable over a wide range of compositionand can be used to form gels in aqueous media or as dispersants andsuspending agents economically.

Generally, the stability of the titanium chelate obtained depends on theratio of a number of moles of Ti to the total number of moles ofchelating agent (i.e., monoethanolamine plus the glycol) contained inthe chelate and the higher this ratio the stronger is the gelling effectof the chelate in aqueous media. Nevertheless, at a high ratio the waterstability of the chelate is impaired in the sense that it partiallyhydrolyzes and precipitates some hydrous titanium dioxide. In additionthe gelling effect is affected by the proportion of monoethanolamine tothe glycol, for instance the higher the molar ratio of monoethanolamineto the glycol the less the chelate is stable to hydrolysis but thegreater its effectiveness as a gelling agent.

Preferably the ratio of the number of moles of the chelating agent(i.e., monoethanolamine plus the glycol) to the number of moles ofTi isfrom 4: l to l l, and more preferably from 4: l to 2.5: l. Preferablythe ratio of the number of moles of monoethanolamine to the glycol isfrom 1:1 to l:3.

One of the most preferable compositions is that containingmonoethanolamine, the glycol and titanium orthoester in the molar ratio1:2: I Naturally, proportions varying slightly from this preferred ratioalso give extremely satisfactory products.

The titanium orthoester which is employed to form the chelates accordingto the present invention are generally those having the formula Ti(OR)in which the R group is an alkyl group containing from two to carbonatoms, preferably two to four carbon atoms. In the general formulaquoted Ti(OR) the R groups can be the same or different. Typicalexamples of titanium orthoesters having this general formula aretitanium tetraisopropoxide, titanium tetrabutoxide and titaniumtetrahexoxide.

The chelates of the present invention can be prepared in a number ofways, for example by mixing the glycol and the monoethanolamine in thedesired proportions followed by the addition of the titanium orthoester.If desired, either the monoethanolamine or the glycol can firstly bemixed with the titanium orthoester followed by the addition of the otheringredient.

The chelates of the present invention are particularly suitable for usein forming a gel in aqueous media. For instance, when mixed with water,a gel is formed which usually will be substantially free of anyprecipitated hydrous titanium dioxide.

When the titanium to chelating agent ratio is low, the time required forformation of the gel may be longer than with chelates where Ti chelatingagent ratio is higher. In this manner, an excellent degree of control ingelation time can be obtained. Low concentrations of active materialtend to give the softer type of gel.

The chelates of the present invention can be used as dispersants tostabilize slurries containing a relatively high proportion of adispersed solid. For instance, the pre-formed chelate may be added to anaqueous dispersion of titanium dioxide pigment to act as a dispersantand stabilizing agent for the titanium dioxide pigment to maintain it inits dispersed form throughout the aqueous medium in a relatively highconcentration. In this case, a gel is not truly formed in the mixtureunless the proportion of the chelate is sufficient to effect this. Theproportion of the chelate employed to obtain a dispersed and stablesuspension depends on a number of factors, for instance on the type ofchelate, on the amount of material to be dispersed and on its type. Butwith suspensions of titanium dioxide pigments it has been discoveredthat only a small proportion of the preferred chelates, say from 0.2 to2 percent by weight of the suspension is required. The suspension is ina form readily amenable to mixing with further ingredients such asthose, for example, to be added to an aqueous titanium dioxidesuspension or slurry for forming into an aqueous emulsion paint. Such afurther ingredient would be, for example, a film-forming polymer to actas a binder for the paint.

The titanium chelates of this invention can also be used to stabilizesuspensions or dispersions in aqueous media of oils, fats and waxes,typical examples being the waxes used in polishes. Such products, bysuitable choice and concentration of titanium chelate, can be renderedthixotropic in nature, with consequent advantages and ease in theirmethod of application and use.

The chelates according to the present invention can contain either oneor more of the glycols referred to previously. For instance, thechelates can comprise a reaction product of monoethanolamine, ethyleneglycol, and propylene glycol together with the titanium orthoester.

The gels formed can be either strong and rigid and only broken down bythe application of a relatively strong shearing force, or weak andreversible. The type depends on the type and concentration of thechelating agent used. The soft gels are usually reversible, that is,when the gel is broken down, a liquid is formed which has roughly thesame viscosity as the original system. On standing, the gel will reform.

The invention is described in the following examples:

EXAMPLE I Into a round bottomed flask fitted with a stirrer, thermometerand water cooled condenser was placed a mixture of 92 gramsmonoethanolamine and 186 grams of ethylene glycol. To the well stirredmixture was added slowly 426 grams of tetraisopropyl titanate. Theapparatus used to contain the titanium ester was suitably protectedagainst the ingress of moisture. Heat was evolved during the reaction.When the reaction had ceased, the titanium chelate product was obtainedas a pale yellow liquid which was then allowed to cool.

Twenty grams of the chelate were added with stirring to 80 mls. ofwater. A clear colorless solution was obtained which set to a rigidtransparent gel within 5 minutes. This gelling action took place atnormal room temperature.

A highly concentrated slurry was prepared by dispersing 650 grams of ananatase titanium dioxide pigment in 350 grams of water containing as adispersant 2.5 grams of calgon. To a 250 gram portion of the solution soprepared was added 2.5 grams of the chelate. A similar 250 gram portionof this slurry was stirred without the addition of the chelate. Afterstanding for 24 hours the untreated slurry had partly settled forming ahard layer on the bottom of the container which was found difficult toredisperse. The slurry which had been treated with the chelate had setto a soft reversible gel in which no sedimentation of the dispersedtitanium dioxide pigment had occurred. lt was observed that the gelcould be broken easily by stirring but reformed on standing. Standingfor a further 50 days produced no sedimentation.

A further 250 gram portion of the titanium dioxide was treated with 1.25grams of the chelate. After standing for 48 EXAMPLE 2 .mls. of water togive a clear colorless solution which set to a firm gel within 2minutes.

A highly'concentrated slurry was made by dispersing 680 grams of rutiletitanium dioxide pigment in 320 grams of water by employing 3.5 grams ofcalgon as a dispersing agent. To a 300 gram portion of this slurry wasadded l.5 grams of the chelate and the slurry formed a gel within 3hours which was free of sedimentation even after being stored for 50days. A similar portion of the slurry but without any of the addedtitanium chelate exhibited a substantial degree of sedimentation afteronly 48 hours storing.

EXAMPLE 3 Various titanium chelates were prepared according to themethod described in Example 1 from tetraisopropyl titanate (TlPT).tetra-normal-butyl titanate (TNBT),

monoethanolamine (MEA) and ethylene glycol, propylene glycol ordiethylene glycol.

The various chelates were tested for their gelling time in a 20 percentaqueous solution and the results together with details of the particularreactants used are given in the following table.

l l 3 I20 TNBT l l 2 5 l 3 6O TlPT Propylene l l 2 5 l l 3 I 2 l 3 24hrs. Slight pptn. I 2 l 2 Slight pptn. TNBT l l 2 2 l l 3 6O TIPTDiethylene l 3 l20 With white ppt. 2 2 5 I20 With some pptn.*

* pptn. precipitation; ppt. precipitate What is claimed is v l. Atitanium chelate comprising the reaction product of monoethanolamine, atitanium orthoester having the formula Ti(OR) in which the R group is analkyl group containing from two to ID carbon atoms, and at least oneglycol selected from the class consisting of ethylene glycol, propyleneglycol and diethylene glycol, the ratio ofthe total number of moles ofmonoethanolamine and of the glycol to the total number of moles ofTibeing from 4: l to l:l.

2. A titanium chelate according to claim 1 in which the said ratio isfrom 4: l to 2.5: l.

3. A titanium chelate according to claim I in which the ratio of thenumber of moles of monoethanolamine to the number ofmoles ofthc glycolis from l:l to l:3.

4. A titanium chelate according to claim I in which the molar ratio ofmonoethanolamine to glycol to titanium orthoester is l :2: l. I

5. A titanium chelate according to claim 1 in \VhlCh the R group is analkyl group containing from two to four carbon atoms.

6. A titanium chelate according to claim 2, wherein the ratio of thenumber of moles of monoethanolamine to the number ofmoles ofglycol isfrom l:l to l:3.

2. A titanium chelate according to claim 1 in which the said ratio isfrom 4:1 to 2.5:1.
 3. A titanium chelate according to claim 1 in whichthe ratio of the number of moles of monoethanolamine to the number ofmoles of the glycol is from 1:1 to 1:3.
 4. A titanium chelate accordingto claim 1 in which the molar ratio of monoethanolamine to glycol totitanium orthoester is 1: 2:1.
 5. A titanium chelate according to claim1 in which the R group is an alkyl group containing from two to fourcarbon atoms.
 6. A titanium chelate according to claim 2, wherein theratio of the number of moles of monoethanolamine to the number of molesof glycol is from 1:1 to 1:3.